1. Field of the Invention
The present invention relates to a thin-film magnetic head having at least an induction-type electromagnetic transducer and a method of manufacturing such a thin-film magnetic head.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought as areal recording density of hard disk drives has increased. Such thin-film magnetic heads include composite thin-film magnetic heads that have been widely used. A composite head is made of a layered structure including a recording head having an induction-type electromagnetic transducer for writing and a reproducing head having a magnetoresistive (MR) element for reading.
It is required to increase the track density on a magnetic recording medium in order to increase recording density among the performance characteristics of a recording head. To achieve this, it is required to implement a recording head of a narrow track structure wherein the width of top and bottom poles sandwiching the recording gap layer on a side of the air bearing surface (medium facing surface) is reduced down to microns or the order of submicron. Semiconductor process techniques are utilized to implement such a structure. Reference is now made to FIG. 25A to FIG. 28A and FIG. 25B to FIG. 28B to describe an example of a method of manufacturing a composite thin-film magnetic head as an example of a related-art method of manufacturing a thin-film magnetic head. FIG. 25A to FIG. 28A are cross sections each orthogonal to an air bearing surface of the thin-film magnetic head. FIG. 25B to FIG. 28B are cross sections of a pole portion of the head each parallel to the air bearing surface.
In the manufacturing method, as shown in FIG. 25A and FIG. 25B, an insulating layer 102 made of alumina (Al2O3), for example, having a thickness of about 5 to 10 xcexcm is deposited on a substrate 101 made of aluminum oxide and titanium carbide (Al2O3xe2x80x94TiC), for example. On the insulating layer 102 a bottom shield layer 103 made of a magnetic material is formed for making a reproducing head.
Next, on the bottom shield layer 103, alumina, for example, is deposited to a thickness of 100 to 200 nm through sputtering to form a bottom shield gap film 104 as an insulating layer. On the bottom shield gap film 104 an MR element 105 for reproduction having a thickness of tens of nanometers is formed. Next, a pair of electrode layers 106 are formed on the bottom shield gap film 104. The electrode layers 106 are electrically connected to the MR element 105.
Next, a top shield gap film 107 is formed as an insulating layer on the bottom shield gap film 104 and the MR element 105. The MR element 105 is embedded in the shield gap films 104 and 107.
Next, on the top shield gap film 107, a top-shield-layer-cum-bottom-pole-layer (called a bottom pole layer in the following description) 108 having a thickness of about 3 xcexcm is formed. The bottom pole layer 108 is made of a magnetic material and used for both a reproducing head and a recording head.
Next, as shown in FIG. 26A and FIG. 26B, on the bottom pole layer 108, a recording gap layer 109 made of an insulating film such as an alumina film whose thickness is 0.2 xcexcm is formed. Next, a portion of the recording gap layer 109 is etched to form a contact hole 109a to make a magnetic path. On the recording gap layer 109 in the pole portion, a top pole tip 110 made of a magnetic material and having a thickness of 0.5 to 1.0 xcexcm is formed for the recording head. At the same time, a magnetic layer 119 made of a magnetic material is formed for making the magnetic path in the contact hole 109a for making the magnetic path.
Next, as shown in FIG. 27A and FIG. 27B, the recording gap layer 109 and the bottom pole layer 108 are etched through ion milling, using the top pole tip 110 as a mask. As shown in FIG. 27B, the structure is called a trim structure wherein the sidewalls of the top pole (the top pole tip 110), the recording gap layer 109, and a part of the bottom pole layer 108 are formed vertically in a self-aligned manner.
Next, an insulating layer 111 made of an alumina film, for example, and having a thickness of about 3 xcexcm is formed on the entire surface. The insulating layer 111 is then polished to the surfaces of the top pole tip 110 and the magnetic layer 119 and flattened.
Next, on the flattened insulating layer 111, a first layer 112 of a thin-film coil is made of copper (Cu), for example, for the induction-type recording head. Next, a photoresist layer 113 is formed into a specific shape on the insulating layer 111 and the first layer 112. Heat treatment is then performed at a specific temperature to flatten the surface of the photoresist layer 113. On the photoresist layer 113, a second layer 114 of the thin-film oil is then formed. Next, a photoresist layer 115 is formed into a specific shape on the photoresist layer 113 and the second layer 114. Heat treatment is then performed at a specific temperature to flatten the surface of the photoresist layer 115.
Next, as shown in FIG. 28A and FIG. 28B, a top pole layer 116 is formed for the recording head on the top pole tip 110, the photoresist layers 113 and 115, and the magnetic layer 119. The top pole layer 116 is made of a magnetic material such as Permalloy. Next, an overcoat layer 117 of alumina, for example, is formed to cover the top pole layer 116. Finally, machine processing of the slider including the foregoing layers is performed to form the air bearing surface 118 of the thin-film magnetic head including the recording head and the reproducing head. The thin-film magnetic head is thus completed.
FIG. 29 is a top view of the thin-film magnetic head shown in FIG. 28A and FIG. 28B. The overcoat layer 117 and the other insulating layers and insulating films are omitted in FIG. 29.
In FIG. 28A, xe2x80x98THxe2x80x99 indicates the throat height and xe2x80x98MR-Hxe2x80x99 indicates the MR height. The throat height is the length (height) of the pole portions, that is, the portions of the magnetic pole layers facing each other with the recording gap layer in between, between the air-bearing-surface-side end and the other end. The MR height is the length (height) between the air-bearing-surface-side end of the MR element and the other end. In FIG. 28B, xe2x80x98P2Wxe2x80x99 indicates the pole width, that is, the recording track width. In addition to the throat height, the MR height and so on, the apex angle as indicated with xcex8 in FIG. 28A is one of the factors that determine the performance of a thin-film magnetic head. The apex is a hill-like raised portion of the coil covered with the photoresist layers 113 and 115. The apex angle is the angle formed between the top surface of the insulating layer 111 and the straight line drawn through the edges of the pole-side lateral walls of the apex.
In order to improve the performance of the thin-film magnetic head, it is important to precisely form throat height TH, MR height MR-H, apex angle xcex8, and track width P2W as shown in FIG. 28A and FIG. 28B.
To achieve high areal recording density, that is, to fabricate a recording head with a narrow track structure, it has been particularly required that track width P2W fall within the submicron order of 1.0 xcexcm or less. It is therefore required to process the top pole into the submicron order through semiconductor process techniques.
A problem is that it is difficult to form the top pole layer of small dimensions on the apex.
As disclosed in Published Unexamined Japanese Patent Application Heisei 7-262519 (1995), for example, frame plating may be used as a method for fabricating the top pole layer. In this case, a thin electrode film made of Permalloy, for example, is formed by sputtering, for example, to fully cover the apex. Next, a photoresist is applied to the top of the electrode film and patterned through a photolithography process to form a frame to be used for plating. The top pole layer is then formed by plating through the use of the electrode film previously formed as a seed layer.
However, there is a difference in height between the apex and the other part, such as 7 to 10 xcexcm or more. The photoresist whose thickness is 3 to 4 xcexcm is applied to cover the apex. If the photoresist thickness is required to be at least 3 xcexcm over the apex, a photoresist film having a thickness of 8 to 10 xcexcm or more, for example, is formed below the apex since the fluid photoresist goes downward.
To implement a recording track width of the submicron order as described above, it is required to form a frame pattern having a width of the submicron order through the use of a photoresist film. Therefore, it is required to form a fine pattern of the submicron order on top of the apex through the use of a photoresist film having a thickness of 8 to 10 xcexcm or more. However, it is extremely difficult to form a photoresist pattern having such a thickness with a reduced pattern width, due to restrictions in the manufacturing process.
Furthermore, rays of light used for exposure of photolithography are reflected off the base electrode film as the seed layer. The photoresist is exposed to the reflected rays as well and the photoresist pattern may go out of shape. It is therefore impossible to obtain a sharp and precise photoresist pattern.
In the sloped region of the apex, in particular, rays of light used for exposure that are reflected off the base electrode film include not only rays in the vertical direction but also those in the slanting or horizontal direction reflected off the slope of the apex. The photoresist is thus exposed to those rays of light and the photoresist pattern more greatly goes out of shape.
As disclosed in Published Unexamined Japanese Patent Application Heisei 6-68424 (1994), Published Unexamined Japanese Patent Application Heisei 6-309621 (1994) and Published Unexamined Japanese Patent Application Heisei 6-314413 (1994), for example, a thin-film magnetic head in which the top pole layer is formed on a flat surface has been proposed. Such a head solves the problem found in cases in which the top pole layer is formed on the apex.
The position of an end of the pole portion opposite to the air bearing surface is hereinafter called a zero throat height position. In the thin-film magnetic head disclosed in Published Unexamined Japanese Patent Application Heisei 6-68424 (1994), the zero throat height position is defined by an end of the top pole. In the thin-film magnetic head disclosed in Published Unexamined Japanese Patent Application Heisei 6-309621 (1994), the zero throat height position is defined by an end of the bottom pole. In the thin-film magnetic head disclosed in Published Unexamined Japanese Patent Application Heisei 6-314413 (1994), the zero throat height position is defined by an end of the top pole and an end of the bottom pole. In any of these heads the end that defines the zero throat height position is a surface orthogonal to the recording gap layer. Therefore, in any of these heads the space between the bottom and top pole layers from the air bearing surface to the zero throat height position has a specific length equal to the thickness of the recording gap layer. This space abruptly increases from the zero throat height position toward the side opposite to the air bearing surface.
In such a structure where the space between the bottom and top pole layers abruptly increases near the zero throat height position, however, the flow of magnetic flux passing through the pole layers toward the recording gap layer abruptly changes near the zero throat height position. As a result, the flux saturates near the zero throat height position, and the electromagnetic transducing characteristics of the thin-film magnetic head are reduced. The electromagnetic transducing characteristics are, to be specific, an overwrite property that is a parameter indicating one of characteristics when data is written over a region on a recording medium where data is already written, and a nonlinear transition shift (NLTS) characteristic, for example.
It is an object of the invention to provide a thin-film magnetic head and a method of manufacturing the same for making a pole portion that defines the track width with accuracy and improving the electromagnetic transducing characteristics.
A thin-film magnetic head of the invention comprises: a medium facing surface that faces toward a recording medium; a first magnetic layer including a pole portion and a second magnetic layer including a pole portion, the first and second magnetic layers being magnetically coupled to each other, the pole portions being opposed to each other and placed in regions of the magnetic layers on a side of the medium facing surface, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least a part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers. The first magnetic layer includes: the pole portion touching the gap layer; a flat portion located at a distance from the gap layer in the direction of thickness of the gap layer, and located farther from the medium facing surface than the pole portion; and a sloped portion connecting the pole portion and the flat portion to each other, the distance from the sloped portion to the gap layer decreasing with decreases in the distance from the sloped portion to the medium facing surface. The at least part of the thin-film coil is located on a side of the pole portion and the sloped portion of the first magnetic layer. The second magnetic layer includes a portion that touches a flat surface including the gap layer and defines a track width.
According to the thin-film magnetic head of the invention, the pole portion and the flat portion of the first magnetic layer are coupled to each other by the sloped portion. As a result, the flow of magnetic flux passing through the first magnetic layer toward the gap layer is smoothly changed from the flat portion to the pole portion. According to the thin-film magnetic head of the invention, at least a part of the thin-film coil is located on a side of the pole portion and the sloped portion of the first magnetic layer. In addition, the second magnetic layer includes the portion that touches a flat surface including the gap layer and defines the track width. It is thereby possible to form the pole portion defining the track width with accuracy.
According to the thin-film magnetic head of the invention, the sloped portion may have a curved surface that faces toward the gap layer.
The thin-film magnetic head of the invention may further comprise an insulating layer that covers the at least part of the coil located on the side of the pole portion and the sloped portion of the first magnetic layer, and has a surface facing toward the gap layer, the surface being flattened together with a surface of the pole portion of the first magnetic layer facing toward the gap layer.
The thin-film magnetic head of the invention may further comprise: a magnetoresistive element; and a first shield layer and a second shield layer for shielding the magnetoresistive element, the shield layers including portions located on a side of the medium facing surface and opposed to each other, the magnetoresistive element being placed between the shield layers. In this case, it is possible that the flat portion of the first magnetic layer is adjacent to the second shield layer, and that an isolating layer is provided between the pole portion and the sloped portion of the first magnetic layer and the second shield layer, the isolating layer isolating the pole portion and the sloped portion from the second shield layer, and defining shapes of the pole portion and the sloped portion. The isolating layer may be made of a nonmagnetic material.
A method of the invention is provided for manufacturing a thin-film magnetic head comprising: a medium facing surface that faces toward a recording medium; a first magnetic layer including a pole portion and a second magnetic layer including a pole portion, the first and second magnetic layers being magnetically coupled to each other, the pole portions being opposed to each other and placed in regions of the magnetic layers on a side of the medium facing surface, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least a part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers. The first magnetic layer includes: the pole portion touching the gap layer; a flat portion located at a distance from the gap layer in the direction of thickness of the gap layer, and located farther from the medium facing surface than the pole portion; and a sloped portion connecting the pole portion and the flat portion to each other, the distance from the sloped portion to the gap layer decreasing with decreases in the distance from the sloped portion to the medium facing surface. The at least part of the thin-film coil is located on a side of the pole portion and the sloped portion of the first magnetic layer. The second magnetic layer includes a portion that touches a flat surface including the gap layer and defines a track width. The method includes the steps of forming a convexity in a region on a base layer of the first magnetic layer, the region corresponding to the pole portion of the first magnetic layer; forming the first magnetic layer on the base layer and the convexity such that the flat portion is formed on the base layer, and a portion covering the convexity forms the pole portion and the sloped portion; forming the gap layer on the pole portion of the first magnetic layer; forming the second magnetic layer on the gap layer; forming the thin-film coil such that the at least part of the coil is located on the side of the pole portion and the sloped portion of the first magnetic layer; and forming the medium facing surface by polishing the first magnetic layer, the gap layer and the second magnetic layer.
According to the method of the invention, the convexity is formed on the base layer of the first magnetic layer, and the first magnetic layer is formed on the convexity. The first magnetic layer including the pole portion, the flat portion and the sloped portion is thereby formed. The flow of magnetic flux passing through the first magnetic layer toward the gap layer is smoothly changed from the flat portion to the pole portion. According to the method of the invention, at least a part of the thin-film coil is located on a side of the pole portion and the sloped portion of the first magnetic layer. In addition, the second magnetic layer includes the portion that touches a flat surface including the gap layer and defines the track width. It is thereby possible to form the pole portion defining the track width with accuracy.
According to the method of the invention, the sloped portion may be formed to have a curved surface that faces toward the gap layer. In this case, the convexity may be formed to have a curved top surface, too.
The method of the invention may further include the step of forming an insulating layer that covers the at least part of the coil located on the side of the pole portion and the sloped portion of the first magnetic layer, and has a surface facing toward the gap layer, the surface being flattened together with a surface of the pole portion of the first magnetic layer facing toward the gap layer.
According to the method of the invention, the convexity or a part thereof may be removed in the step of forming the medium facing surface.
According to the method of the invention, the convexity may be made of a resist layer that has received heat treatment or a metal plating layer.
The method of the invention may further include the step of forming: a magnetoresistive element; and a first shield layer and a second shield layer for shielding the magnetoresistive element, the shield layers including portions located on a side of the medium facing surface and opposed to each other, the magnetoresistive element being placed between the shield layers. In this case, the flat portion of the first magnetic layer may be located adjacent to the second shield layer, and an isolating layer may be provided between the pole portion and the sloped portion of the first magnetic layer and the second shield layer, the isolating layer isolating the pole portion and the sloped portion from the second shield layer, and forming the convexity and defining shapes of the pole portion and the sloped portion. The isolating layer may be made of a nonmagnetic material.
Other and further objects, features and advantages of the invention will appear more fully from the following description.